This invention relates to transportation of sensors and instruments inside water pipes, and more particularly to a passive robot with a soft, squeezable body that can maneuver through sharp 90 degree bends and T-junctions in pipes while carrying a leak detection sensor.
Underneath the streets in every city around the world, water pipe systems distribute this precious resource quietly and their important problems are usually unnoticed. One such problem is pipe leakage. It has been reported that around 20% of the clean water supply in almost all countries around the globe is lost due to leaks [1], [2]. In regions of water scarcity such as Saudi Arabia, the leak rate is even higher, at more than 30% [3]. By reducing leaks, a society can meet more water demand with the current production capacity. Leak reduction can directly alleviate the global clean water shortage which is going to be more severe as population grows.
Water leaks are difficult to find. While water pipe bursts happen occasionally, small leaks exist all the lime in every mile of underground water pipes. Those small leaks account for most of the water losses, and they can develop into big leaks and eventually pipe bursts. The typical above-ground manual detection procedure used by almost all water authorities is not effective in finding small leaks, especially where the pipe is hard to reach, for example, underneath a building. In-pipe leak detection methods with cameras, acoustic systems and pressure sensing systems can find the location of those leaks more reliably and accurately. Researchers have been developing pressure gradient based in-pipe leak sensors [4], [5]. They use membranes to detect the suction force generated at leaks. It is particularly good for finding small leaks in low pressure, small diameter pipes.
A good in-pipe leak sensor is only useful when a mobile platform can carry it through the water pipes. The city water distribution systems commonly consist of small diameter pipes between 50 to 150 mm (2-6 in). There are many T-functions and elbows. They are operating with water flows inside most all the time. A mobile platform must be able to go through small diameter pipe systems with T-junctions and elbows, under flow condition. Moreover, typical leak sensors use membranes to detect leaks, and those membranes must be kept within a fixed distance to the pipe wall in order to detect leaks. The platform then must have position and orientation stability. The existing in-pipe platforms fail to meet both criteria at the same time. On one end of the spectrum, free floating system such as the Smartball [6] can follow the water flow through pipes with elbows. In-pipe swimming robots such as [7] can actively turn at T-junctions and elbows. Both systems are small and move in pipe without contacting the pipe walls. However, they are easily affected by turbulence in the pipe. They cannot maintain the proper position and orientation of the leak sensor. On the other end, Pipeline Inspection Gauges (PIGs) are flow driven robots; they slide on the pipe walls. They can carry ultrasonic transducers, magnetic flux leakage sensors, and other sensors with similar position and orientation stability requirements, through pipelines [8]. Regular PIGs are rigid and single-piece. Some others are more like trains, having multiple sections connected with joints, such as [9], Single-piece PIGs cannot make sharp turns around pipe elbow but train-like PIGs can. However, all PIGs have been developed for larger diameter pipes; ones for small diameter pipes are difficult to build.
In addition, the insertion and removal of existing robots into and out of water pipes typically requires installation of special entry and exit points. This can be cost prohibitive. The preferred option is to insert robots into pipes and take them out from existing pipe infrastructures, such as fire hydrants. The fire hydrant is essentially a 90-degree bend followed by a T junction connecting to the water pipes. It is difficult for existing rigid, single-piece or multi-sectional robots to go through those bends and T junctions. Without the robots' capabilities to enter and exit water pipes via fire hydrants, it expensive to deploy them in the real water pipes.
It is therefore an object of the invention to provide a robot for carrying a leak sensor through a small diameter, complicated water pipe system including elbows and T-junctions along with mild obstacles while maintaining position and orientation stability for the leak sensor it carries.